1. Field of the Invention
This invention relates to the processing of nuts, and in particular to both the removal of the pellicle from nut kernels and the roasting of the kernels.
2. Description of the Prior Art
The removal of pellicle from nut kernels is an important step in the processing of many varieties of nutmeats. The pellicle is the thin skin encircling the kernel (or endosperm). By removing pellicle, one enhances the character of the nutmeats for a variety of reasons, including facilitating the addition of flavorings or coatings, dicing, forming the kernel into nut paste or nut butter, and generally improving the pleasure of eating the shelled nuts out of hand.
Pellicle is comprised largely of cellulose in combination with a number of minor constituents present in differing amounts from one nut variety to the next. In some varieties, these minor constituents cause the pellicle to be tightly affixed to the kernel and difficult to remove. This is a particularly acute problem, for example, in Brazil nuts and American varieties of hazelnuts, more so in fact than in European hazelnut varieties. Known methods for removing such pellicle involve harsh chemical or physical treatments which either damage the kernels or detract from the taste. The chemical treatments generally involve an immersion in caustic soda or other alkaline solution, followed by an acid neutralization. Examples of such processes are disclosed in Stagmeier, U.S. Pat. No. 2,156,406, May 2, 1939, and Edes, U.S. Pat. No. 2,273,183, Feb. 17, 1942. These treatments are detrimental to the flavor of the final product and result in kernels of unnatural color. An example of a physical treatment is disclosed in Schoolcraft, U.S. Pat. No. 2,651,345, Sept. 8, 1953. This involves the use of a high pressure water spray to remove the pellicle, and is also used in conjunction with chemical treatments. In order to be effective, however, the physical treatment is so strong that it often results in physical damage to the kernel itself and still results in a nonuniform product due to incomplete pellicle removal. Such treatment may also result in emulsification or saporification of the outer layers of the oil-bearing endosperm. Furthermore, such treatment has a high energy consumption and requires expensive equipment.